Distortion?

 Is it safe to have the gain turned all the way up,  with the head unit set at around half to three quarters volume, if there is no distortion?

The gain on an amp is not just a secondary volume knob.  The gain knob is there to maximize your signal-to-noise ratio.  If the knob is too low then your not pulling enough signal from your headunit.  If the gain is too high then you'll end up not with distortion in your speakers, but with extra noise - meaning even if you lower your volume all the way you'll still hear sort of a hiss.  If your preouts are 4 volts then set your gain to 4 volts.  This is where you'll get the most signal with the least amount of noise.

The HU is an Alpine CDA-9827 with the internal amp turned off, the external amp is a fosgate 501x,  the sub amp is a fosgate 550s pushing two kicker comp 12's. The amp enclosure has two fans on opposing sides one pushing, the other pulling, to get cross ventilation. The 501x is powering four Infinity Refrence 5 1/4's.  the front channel also has two 3.5 Legacy tweeters, will add two more to the rear. Front channels are @2ohms and the rear is @4ohms for now. having difficulty finding 3.5 tweets that can handle 65 wrms.

Thanks for all your help!

                                         T

Audiobahn (supposedly) make 3.5" speakers that handle 60 watts RMS. I hear they exaggerate their ratings and specs. Check out this site for futher info.

http:///.com/dll? ViewItem&category=14937&item=3093291314

For arguements sake throw wattage out the window, it will not tell you how loud it goes nor how it will sound. Just because the speaker says it is 65 watts and your amp says it is 65 watts does not mean a thing. Your amp will make a varying amount of power for a speaker to handle. You should be looking for a speaker that sounds good, is fairly efficient and then look at the "wattage" rating. You hear in decibels, not watts. I happen to tlike the MB Quart 3.5" speakers. They sound great, a pure titanium tweeter for nice high and smooth top end and they handle power quite well. What will kill a speaker of this size is either clipping of the amp or cd player, or forcing the speaker to play a frequency that is beyond it's appliciation. Point here is that yes it too can play 100hz bass notes, it just cannot do it with the same force as a 10" sub. Thus a crossover set to 200hz or higher is usually a good safety gate for use on a speaker of this size.

The gain control on the amp is a matching device only. It allows the amp to be used with different types of cd players that have different output voltages. It is something totally different that the voltage from a battery or remote on signal, do not confuse these. The amp seems to make more power if the gain is turned up correct, this is because you are feeding more signal into the amp, however think of the gain as a redline for the engine. Go above redline and bad things will happen. The redline for amp, as set by the gain is called the point of clipping. Once this happens the amp has reached full output and is now exceeding its design, when this happens it produces a clipped (distorted) signal for the speaker to reproduce.

If you have a high output voltage, there is a large amount of signal and the gain can be turned down so that the redline is not hit right away. If you have a low output voltage, the gain is usually turned up as there is not much signal to be used so that the redline is also not hit right away. In the case of your Alpine cd player that claims to havea 4 volt preout, it is actually much close to the 1.5 volt area on the sub channel preout, thus the gain is usually kept sky high on the amp so that you can get some kind of respectable output from the subs. The danger here is clipping (redline), when that amp runs out of clean power, it distorts and passes on that signal for the speaker to reproduce. Clipping will affect a smaller speaker much faster than a larger speaker like a sub. An amp produces the same amount of power regardless of where the gain is set at. It can reach full power when the gain is turned all the way down or all the way up, the trick is to set the gain properly and accurately match it to the voltage from the cd player so as to avoid clipping.